1. Technical Field
This invention relates to all-reflective optical systems and, more particularly, to an afocal reimaging and image derotating all-reflective optical system.
2. Discussion
Optical systems located on stabilized gimbals for pointing purposes, which provide imagery to detector arrays located off gimbal, require image derotation devices to maintain constant image orientation as the gimbal is articulated. Relevant art devices utilized in this area ordinarily separate the reimaging and derotation functions into two optical systems. One, for reimaging, utilizing lenses and/or powered mirrors and another for derotating, utilizing prisms and/or planar mirrors.
Relevant art derotation devices utilizing prisms are well known. Some of the known prisms which are utilized for derotation are Pechan, Reversion, Harting-Dove, and Abbe Type A and B. Also, a known reflective derotation device is a K mirror arrangement which utilizes three planar mirrors arranged in a K type configuration. These devices can be very large, heavy, require long path lengths, and do not reimage the viewed scene.
Likewise, known in the field are various afocal reimaging optical systems of refractive and reflective construction. While these devices provide satisfactory imaging or reimaging, none function well as a derotation device providing useable scene and pupil image quality.